Dieldrin was developed as an alternative to DDT and has proved to be a highly effective insecticide. It was very widely used during the 1950s to early 1970s. Endrin is a stereoisomer of dieldrin.

However, it is an extremely persistent organic pollutant; it does not degrade easily. Furthermore it tends to biomagnify as it is passed along the food chain. Long-term exposure has proven toxic to a very wide range of animals including humans. For this reason it is now banned in most of the world.

It has been linked to health problems such as Parkinson's disease, breast cancer, and immune, reproductive, and nervous system damage. It can also adversely affect testicular descent in the fetus if a pregnant woman is exposed to Dieldrin.